What is the difference between mass balance and energy balance?
Mass balance tracks the physical matter entering and leaving the body, including food, water, oxygen, carbon dioxide, and waste; energy balance tracks metabolizable calorie intake versus expenditure. Negative energy balance promotes use of stored fuel, while mass balance accounts for where the resulting atoms and other body matter go.
The ledgers obey conservation laws but remain dimensionally separate. A kilogram cannot be subtracted from a kilocalorie.
Are mass balance and material balance the same?
Yes, material balance and mass balance commonly refer to the same conservation-of-matter accounting framework, although a material balance may track individual chemical species as well as total mass. On this site, the term is restricted to human metabolic inputs, outputs, and body storage rather than industrial process calculations.
Species-level accounting is useful for triglyceride oxidation because carbon, hydrogen, and oxygen atoms can be followed into carbon dioxide and water.
Which equation should you use for weight loss?
Use energy balance to estimate changes in body energy stores and mass balance to explain matter flows and observed mass change. For practical planning, begin with energy intake and expenditure, then interpret scale changes using body composition, water, glycogen, sodium, digestive contents, and a multi-week trend.
No single simplified equation precisely separates all tissues in a free-living person.